Cryosurgical probe

ABSTRACT

A small, self-contained, disposable cryosurgical probe has a pencil-like housing with a refrigerant-containing cartridge in the housing and a hollow tip projecting from the housing. A small diameter capillary tube has one end in the housing opposite the cartridge and its other end extending into the tip with the intervening length of the tube formed into a multi-turn coil. The refrigerant is conducted from the cartridge through the tube to the probe tip and the temperature of the refrigerant is stabilized so as to maintain a substantially uniform mass flow rate of refrigerant through the tube to the tip.

United States Patent [191 Crandell et al.

[451 Oct. 7, 1975 1 CRYOSURGICAL PROBE [21] Appl. No.: 475,787

OTHER PUBLlCATlONS Staebler, Thoery and Use of a Capillary Tube forLiquid Refrigerant Control, IN Jour. A.S.R.E., Jan.

Marcy, Pressure Drop With Change of Phase in a Capillary Tube, IN Jour.A.S.R.E., Jan. 1949. p. 53.

Staebler, Capillary Tubes, Published as See. 2 of RefrigeratingEngineering for Jan. 1950, p. 1 used.

Primary Examiner-Channing L. Pace Attorney, Agent, or Firm-Cesari andMcKenna [57] ABSTRACT A small, self-contained, disposable cryosurgicalprobe has a pencil-like housing with a refrigerant-containing cartridgein the housing and a hollow tip projecting from the housing. A smalldiameter capillary tube has one end in the housing opposite thecartridge and its other end extending into the tip with the interveninglength of the tube formed into a multi-turn coil. The refrigerant isconducted from the cartridge through the tube to the probe tip and thetemperature of the refrigerant is stabilized so as to maintain asubstantially uniform mass flow rate of refrigerant through the tube tothe tip.

18 Claims, 4 Drawing Figures There are in use today some self-containedprobes which do not require a separate fluid supply. Basically, theseunits consist of a housing containing a reservoir of a suitablerefrigerant such as Freon gas, maintained as a liquid under highpressure. When it is desired to use the probe, a diaphragm in the wallof the reservoir is ruptured, allowing the refrigerant therein to flowinto a chamber where the Freon evaporates and in the process coolsitself and the inner end of the probetip inside the chamber. The workingend of the tip projecting from the chamber is then cooled by thermalconductiQn.

While these conventional disposable probes do work, their operation isnot entirely satisfactory. Their main problem stems from the fact thatthe working end of the probe tip is not cooled directly by therefrigerant but rather by thermal conduction along the entire length ofthe tip. Since the cross-section of the tip is quite small, especiallyin the case of ophthalmic probes, it takes ten seconds or more to coolthe tip end to the requisite working temperature of, say, C.

Some prior probes are also disadvantaged in requiring a relatively largesupply of refrigerant. This makes the probe body excessively large,e.g., 1 inch in diameter and 4 inches long, and therefore unwieldy anddifficult to manipulate over the patients eye.

Other prior self-contained probes are overly expensive and have arelatively short operating time which may encourage the doctor to rushsurgical procedures. Still other probes sometimes forcefully dischargeforeign material from the punctured diaphragm which can cause injury tothe doctor or the patient. All of these factors have militated againstthe wider use' and acceptance of self-contained disposable cryosurgicalprobes.

SUMMARY OF THE INVENTION The present invention aims to provide aselfcontained cryosurgical probe which is small, compact and easy tohandle. I

A further object of the invention is to provide a probe of this typewhich, whenactivated, brings the probe tip to the operating temperaturein a few seconds.

Another object of the invention is to provide a selfcontained ophthalmicprobe which can maintain its working temperature for a relatively longtime.

Yet another object of the invention is to provide a probe of thisgeneral type which-is relatively inexpensive to make and which thereforemay be thrown away after each operation.

A further object of the invention is to provide a selfcontained probewhich though having a very small diameter working tip is able to developand hold a relatively large iceball at'its working temperature.

Still another object of the invention is to provide a self-containedprobe which can be recharged and reused.

Still another object isto provide a disposable cryosurgical ophthalmicprobe having a relatively long shelf life.

Another object of the invention is to provide a selfcontained probe ofthis type whose refrigerant supply can be conserved following actuationof the probe to accommodate temporary interruptions in the surgicalprocedure.

Other objects will in part be obvious and will in part appearhereinafter.

The invention accordingly comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the following detailed description, and the scope of theinvention will be indicated in the claims.

In general, the present cryosurgical probe consists of a thin,pencil-like housing containing a cylindrical cartridge filled with asuitable pressurized refrigerant such liquid Freon. The refrigerant ismaintained at room temperature and is retained within the cartridge by aspecial removable plug, or other fluid tight seal, recessed into the endof the cartridge, to be described in detail later.

The probe tip is positioned in the end of the housing opposite thatplug. It consists of a relatively small diameter tube having one endsecured in the end of the housing and projecting an appreciable distancefrom the housing, the exterior end of the tube being closed.

A cylindrical plunger is positioned between the plug and the probe tip.The plunger projects into the endof the cartridge somewhat and a slidingseal is provided between the plunger and the cartridge wall. A longlength of capillary tubing is coiled up inside the plunger. One end ofthe tubing communicates with the end of the plunger opposite the plug,and the opposite end of the tubing projects from the other end of theplunger into" the hollow probe tip almost to its closed end.

The refrigerant cartridge is mounted in the housing so that it can bemoved along the housing axis toward the plunger by means of apush-button installed in the end of the housing remote from the tip.When the button is depressed, the cartridge is urged toward the plungerwhich thereupon pushes the plug into the cartridge until the sealbetween the plug and the cartridge wall is broken. The Freon then flowsinto the capillary tube within the plunger and issues from the endthereof adjacent the working end of the probe tip. As it leaves thecapillary tube, the Freon evaporates and expands and becomes cold in theprocess thereby directly cooling the probe tip. The Freon exhausts as agas from the tip through the spaces between the housing and the plungerand cartridge walls, and leaves the probe through the crack around thepush-button.

The working end of the probe tip is brought to operating temperaturequite quickly because the cooling process does not depend upon thermalconduction along the tip to cool the tip end. Rather, the Freon isdelivered directly to the probe tip and thus cooling takes place rightat the working end of the tip.

The probe is able to operate consistently for a relatively long periodof time, e.g., 3-5 minutes, on the moderate amount of refrigerantcontained inside the cartridge e.g., 3cc, of which 2.3cc is liquid atroom temperature, because the probe maintains two phase flow of Freonthrough the capillary tube to the probe tip. In other words, the Freonflows through the capillary tube as a saturated vapor and liquid so thatcooling at the tip is caused primarily by evaporation of the refrigerantright at the tip.

This two phase flow is achieved by isolating and insulating the Freonflowing through the capillary tube from the'cold gas exhausting from thetip, thereby inhibiting regenerative cooling of the incomingrefrigerant. Although it may be accomplished in other ways,

the isolation is accomplished by bringing the room temperature liquidFreon into intimate contact with the capillary tube coiled inside theplunger. Thus when the probe is activated by depressing the push-button,liquid Freon is allowed to flow down into the plunger so that thecapillary tube therein is bathed in the room temperature liquid. Sincethe specific volume of the fluid flowing to the tip is kept relativelyhigh in this manner. the probe tip can be maintained at its -30C.working tem perature for as long as 3 to minutes. quite enough time tocomplete a cataract extractin operation.

On the other hand, if the refrigerant flowing through the capillary tubeto the tip is not isolated in this fashion from the cold exhaust gas,the incoming refrigerant would be cooled so that it would flow to thetip primarily in its liquid phase. The flow of the liquid refrigerant tothe tip would then be significantly more than required to offset theheat load upon the tip from without, and the tip and chamber would beflooded with excess refrigerant which would therefore be wasted.

If necessary, the doctor can conserve the refrigerant supply in thepresent probe if he should activate the probe prematurely or requires abrief interruption in the operation. More particularly he may point theprobe tip upwards causing the liquid refrigerant to drain from theplunger. The incoming Freon is now in its gaseous phase so that its massrate of consumption drops. If the doctor now points the tip downwardagain, the incoming Freon becomes a combination of a saturated vapor andliquid again and the tip cools to its working temperature in 2 or 3seconds, whereupon the operation can beresumed.

Even though the subject probe has a very small diameter tip, only on theorder of 0.062 in. its cooling capacity is such that it can form aniceball large as 3.5 mm in diameter. Since the tip presents so littlesurface area, the iceballs formed thereon sometimes have a tendency tofall off. Accordingly, the working end of the tip is intentionallyabraded or roughened to increase the adherence of the iceball to thetip.

The subject probe is intended primarily to be a disposable item becauseits cost is so low. However, provision can be made for replacing theFreon cartridge so that the probe can be reused. All of the probe partsare able to withstand ethylene oxide gas so that the probe can beresterilized prior to each use. Also provision can be made for stoppingthe exhaust of refrigerant from the probe in order to build up a backpressure at the probe tip to cause the probe tip to defrost. Thisfeature facilitates detachment of the probe from tissue. These aspectsof the probe will be described in greater detail later.

With its advantages of small size, light weight rapid freezing followingactuation, and long running time, the present probe should prove to bean invaluable surgical instrument particularly for delicate eyeoperations such as a cataract removal or removal of foreign materialfrom the vitreous humor.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of thenature and objects of the invention, reference should be had to thefollowing description taken in connection with the accompanying drawing,in which:

FIG. 1 is a perspective view of a self-contained cryosurgical ophthalmicprobe made in accordance with this invention;

FIG. 2 is a sectional view on a larger scale of the FIG. 1 probe beforeactuation;

FIG. 3 is a fragmentary view with parts broken away on a still largerscale showing elements of the probe in greater detail after the probe isactivated, and

FIG. 4 is a perspective view on an even larger scale showing the probetip in greater detail.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I of thedrawing. the probe shown generally at 10, is comprised of a pencil-likeplastic housing 12 approximately 5.5 inches long and 0.4 inch in outsidediameter. A tubular tip 14 projects from the lower end of the housing.The working end of the tip at 14a is closed. Shaped and roughened fingerengaging surfaces 15 are provided on the outside of housing 12 near thetip 14.

Probe 10 is activated by depressing a push-button 16 located at its endremote from tip 14. In 2 to 3 seconds following depression of button 16,the probe tip 14a becomes cooled to the desired working temperature,e.g. 30C. In normal use. the tip 14a will remain at that temperature forat least 3 minutes which is ample time to complete a cataract extractionprocedure even with complications.

Following activation of the probe. freezing at the tip can beinterrupted temporarily by orienting the probe so that the tip pointsupward. The tip will then re-freeze when the probe is returned to itsdownward orientation. This feature permits the doctor to extend theeffective running time of the probe should he activate it prematurely orencounter some reason for briefly delaying a surgical procedure.

Turning now to FIG. 2, housing 12 contains a cylindrical metal cartridge18 containing a supply of refrigerant, in this case liquid Freon, undera suitable pressure of, say, 75 psi at room temperature (72F). CartridgeI8 is charged with Freon, say, by way of its necked-down end 18a. Thatend of the cartridge is then sealed off, for example, by means of arecessed plug 22. The other end of cartridge I8 is positioned inside thehousing 12 opposite the inner end 16a of button 16.

Cartridge I8 is dimensioned so that it can shift axially in housing 12when button 16 is depressed. Furthermore, provision is made for latchingthe cartridge in its shifted position. This latch can be a latchingarrangement such as is found in conventional ballpoint pens. or it canbe as shown in FIG. 2, a stamped metal +-shaped claw 24 having resilientarms 24a which dig into the inside wall of housing 12 and resist thereturn of the cartridge to its original position before button I6 wasdepressed.

Plug 22, which seals cartridge 18, is generally cylindrical and isprovided with a circumferential groove 26, midway along its length, inwhich seats an O-ring seal 28. After the cartridge 18 is charged withFreon. the plug 22 is inserted to seal off its end 18a. The plug isretained in position despite the 75 psi charging pressure in thecartridge by a pair of flexible, resilient arms 32 supported by a stem27 projecting from the end of plug 22 inside the cartridge. These armssnap out laterally when the plug is inserted and engage behind theshoulder 34 formed where the necked-down cartridge portion begins. whenthe plug 22 is properly seated, it is recessed somewhat into cartridgeportion 18a, as is best been in FIG. 2.

The probe tip 14 consists of a cylindrical stainless steel tube 0.062inch in outside diameter and extends 0.5 inch from the housing. One endof the tube extends into the housing through an opening 38 providedtherefore, and is secured there by any commercial means. The exposed endof the tube corresponding to the working tip end 14a is closed.

Turning for a moment to FIG. 4, the inner end of tip 14a isintentionally slit to form four small tabs 14b, which splay out andresiliently engage the inside wall of the housing to prevent the tipfrom rotating and translating relative to housing 12. Although some suchrotation can be tolerated in the case of a straight tip, it causesinconvenience when the tip is curved. This is because downward pressureon the probe would then apply a torque to the tip which might cause thetip to rotate the working end 14a away from the tissue being frozen.

The closed end of the probe tip at 140 is textured or roughened as gestseen at 42 in FIG. 4. This texturing increases the surface area at 14aand provides minute indentations to which an iceball formed on the endof the tip can adhere. If the tip is not textured in this way, aniceball formed thereat might tend to fall off because the diameter ofthe tip is so small, and such little contact area exists between the tipand the iceball.

Also, to localize the point on the tip 14 where tissue can adhere, asilicone sleeve 44 is shrunk fit onto the tip covering it except for itsworking end 14a.

Referring again to FIG. 2, positioned between the cartridge plug 22 andthe inner end of tip 14 is a plunger assembly shown generally at 52.Assembly 52 includes a generally cylindrical tube 54 having acircumferential groove 56 in its outer wall for accommodating O-ringseal 58. The tube 54 is arranged so that it slidably fits insidecartridge portion l8a'with the O- ring providing a fluid-tight sealbetween the tube and the cartridge wall in the presence of thepressurized refrigerant.

During the shelf-life of the probe, one end of the plunger tube 54 ispositioned within cartridge portion 18a as shown in FIG. 2, while itsother end butts against a shoulder 12a formed in housing 12 adjacent tip14 which prevents movement of the plunger toward the tip.

Plunger 52 also supports a long, small-diameter No. 32 gauge stainlesssteel capillary tube 62. The tube has an inside diameter of 0.004 inchand is on the order of 1 foot in length. Most of the tube is containedas a 0.3 inch long, 0.117 inch diameter coil 62a seated in a bore 64 inthe outer end of tube 54. A straight capillary tube segment 62/) extendsfrom the outer end of the coil into probe tip 14 almost to its workingend 1411. A suitable epoxy potting compound 66 seals off the open outerend of bore 64.

A second straight tubing segment 620 extends from the inner end of coil620 into an axial passage 68 leading from bore 64 to a second bore 72 atthe other end of plunger tube 54.

A plug 74 of a suitable filter material such as porous polyethylene isinserted into bore 72 adjacent to the open inner end of the capillarytube 62 to prevent any foreign matter from entering and possiblyclogging the tube. I

Referring now to FIGS. 2 and 3, when it is desired to activate probe 10,the button 16 is depressed. This movement of the button shifts cartridge18 axially within housing 12 and urges it towards plunger 52 whoseposition is fixed. The inner end of the plunger is pressed against plug22 and pushes the plug sufficiently into the cartridge to break the sealbetween the plug and the cartridge wall, thereby releasing thepressurized Freon in the cartridge as shown in FIG. 3. The Freon flowsthrough the filter plug 74 and the capillary tube 62 and issues from thetube end inside tip 14a. Very little work is done by the Freon coolingthe cartridge 18. Rather, the refrigerant undergoes both expansion andevaporation cooling in the cavity right at tip end 14a, so that the tipis brought to its working temperature of at least 30C in only 2 or 3seconds. The refrigerant exhausts as a cold gas from the tip through thespace between the housing wall and cartridge l8 and plunger 52 andleaves the probe through the circular crack in the housing around theactuating button 16.

As best seen in Fig. 3, liquid Freon still at room temperature is freeto flow through the space between the wall of passage 68 and tubingsegment 620 so that it bathes the capillary tube coil inside the bore.Thus the liquid serves as an insulating and isolating blanket betweencoil 62a and the cold gas exhausting from tip 14. Consequently, there islittle if any regenerative cooling of the incoming Freon with the resultthat two phase flow is maintained rather than all liquid flow during theentire operating time of the probe. This factor gives the probe arelatively long running time, e.g. 3 to 5 minutes, even though thecartridge 18 has a relatively small volume, e.g., 3 cc, and thecapillary tube 62 has a bore which is large enough (e.g., 0.004 inch) sothat plugging is not a problem. In this connection we should mentionthat if the refrigerant supply has a volume much more than 12cc, theoverall probe becomes unduly large and unwieldy and therefore difficultto use.

If only liquid flows through the capillary tube 62 a relatively largesupply of refrigerant is required, to provide cooling for 3 minutes,thus necessitating a much larger cartridge. This, in turn, would makethe overall probe large and unwieldy as some prior selfcontained probes.On the other hand, if the refrigerant flows to the probe tip only as agas, cooling occurs primarily by the Joule Thompson effect and expansionrather than by the more efficient evaporation phenonemon so that thecooling of theprobe tip is not sufficient to overcome the heat loadimposed on the probe at normal room temperatures.

The small lightweight self-contained disposable probe with which we areconcerned here has a limited refrigerant supply which must maintain theprobe tip at the required low temperature for the required time. To makemaximum use of this limited supply, the refrigerant is delivered rightto the working end of the probe tip where the tip end is cooled directlyprimarily by the process of evaporation which is a most efficient modeof cooling.

Also, since the mass flow rates of the refrigerant are drasticallydifferent depending upon whether the refrigerant is in its liquid orgaseous phase (the ratio is at least 5 to l), the temperature of theliquid refrigerant flowing to the tip is stabilized so that therefrigerant enters the chamber inside the tip as a two-phase fluid whenthe probe is activated initially and during its entire operating time.In other words, the point in the capillary tube at which the superheated refrigerant boils or evaporates is kept more or less the same sothat the mass flow rate of the refrigerant to the tip also remains thesame and is predictable from probe to probe. This flow rate issufficient immediately upon actuation of the probe to cool the tip to atemperature low enough to cause the tip to adhere to tissue in a fewseconds. Further the flow rate does not increase materially due toregenerative cooling of the incoming Freon by the cold gas exhaustingfrom the probe and does not decrease appreciably due to a normal heatload on the probe tip.

The point in the capillary tube at which the liquid Freon boils cannotbe determined exactly. Based on empirical results, if boiling occurs toonear the beginning of the tube, the mass flow rate of the refrigerant istoo low to sustain a low enough tip temperature in a room temperatureenvironment. On the other hand if it occurs too near to the end of thetube, the mass flow rate is excessively high so that while the tip iscooled quite adequately, all of the Freon in the cartridge is used uptoo fast so that the probe does not have a 3 minute operating time.

The best estimate is that boiling should occur approximately 80% alongthe length of the capillary tube 62 for best results in terms of tiptemperature and operative time.

In the present probe the temperature of the incoming Freon is stabilizedby isolating and insulating it from the cold gas exhausting from theprobe tip. This exhaust gas would otherwise cool the incomingrefrigerant as the probe continues to run thereby shifting the point inthe tube 62 at which boiling occurs toward the end of the tube. This inturn would increase the mass flow rate of the refrigerant and shortenthe running time of the probe. While the means of isolation may takedifferent forms, it is accomplished here conveniently by bathing thecoil 62a in room temperature liquid Freon from cartridge 18. It is alsofeasible to isolate the tube by potting it in a thermally insulatingmaterial.

With the present probe, the supply of refrigerant can be conserved oncethe probe has been activated. If the doctor is not quite prepared towork on the patient for one reason or another after he depresses button16, he can orient the probe so that its tip end 14a points upwards. Theliquid Freon bathing coil 62a then flows back into cartridge and onlygas is available to flow to the tip 14a and its rate of consumption ismuch less than it would be if it flowed as a two phase saturatedvapor-liquid system. In fact, the flow of Freon as a gas can continue aslong as 5 or 6 minutes. This means that if the doctor holds the probeupright for even as long as a minute or more and then starts or resumesa cataract removal operation by pointing the probe downwards, the tip14a will reach its working temperature in 2 or 3 seconds and ample Freonwill still remain in cartridge 18 to run the probe for 2 to 3 minuteswhich is ample time to complete a cataract removal procedure even iffurther complications arise.

Thus despite its small, slim profile, the present probe contains therequisite amount of refrigerant to maintain the probe at the properoperating temperature for the normal time required for a cataractremoval operation or a vitreous removal procedure. The probe islightweight so that it can be manipulated easily and precisely by thedoctor, yet its cost of manufacture is low enough so that the unit canbe considered disposable.

In situations where it is necessary to store the fully charged probe fora long period before use, it may be desirable to seal cartridge 18 bymeans of a brass diaphragm instead of a plug 22. In this event the inneredge of the plunger tube 54 may be sharpened so that when the button 16is depressed, the sharpened edge cuts through the diaphragm and releasesthe refrigerant.

Also it may sometimes be preferable to re-use the probe, in which casethe housing 12 would be com-.

prised of two sections threaded together. When the refrigerant incartridge 18 is expended, the housing sections would be taken apart andthe cartridge 18 pulled away from the plunger 52 which would be retainedin the lower end of the housing. Then a new capsule 18 would be inserteddown on the plunger after which the housing sections would be screwedtogether. Following re-sterilization, the probe would then be ready forreuse.

lt may also be desirable to be able to heat the probe tip to facilitateits detachment from tissue. This can be accomplished in the presentprobe by providing a flexible seal over the button 16 in the upper endof the housing which would permit the button to be depressed, yetprevent gas from exhausting through the crack between the button and thehousing. Then a separate valved exit port is provided within the housingwhich would remain open when it is desired to cool the probe tip. Whenthe surgical procedure is completed and it is desired to release the tipfrom the tissue, this valve would be closed resulting in a back pressurebuild-up inside the probe tip which warms the tip sufficiently to meltthe tissue contacted by the tip.

It will thus be seen that the objects set forth above among thosemadeapparent from the preceding description are efficiently attained andsince certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing should be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed.

We claim: 1. A self-contained cryosurgical probe comprising A. apencil-like housing, B. a refrigerant-containing cartridge slidablypositioned in the housing, Cv a hollow, thermally conductive tipprojecting from one end of the housing, D. a plunger assembly positionedwithin the housing between the cartridge and the tip, E. a smalldiameter capillary tube connected to the plunger assembly, said tubehaving 1. one end thereof communicating with the plunger end adjacent tothe cartridge,

2. its other end positioned inside the tip near its outer end, and

3. a substantial length intermediate its said ends formed into a smalldiameter multi-turn coil,

F. means on the plunger assembly for opening the cartridge when thecartridge is slid toward the plunger assembly, and

G. means for sliding the cartridge toward the plunger so that theplunger opens the cartridge and releases the refrigerant which thereuponflows through the capillary tube to the probe tip and cools the tip.

2. The probe defined in claim 1 wherein A. the cartridge has a removableplug in the end of the cartridge opposite the plunger, and B. theplunger assembly opens the cartridge by pushing the plug into thecartridge. 3. The probe defined in claim 2 5 A. wherein the cartridgehas an internal shoulder in the end thereof containing the plug, "and B.the plug has flexible resilient arnis formed on the end of the pluginside the cartridge, said arms engaging behind the shoulder to preventblow out of the plug due to pressure inside the cartridge aboveatmospheric. 4. The probe defined in claim 1 A. wherein the capillarytube coil is positioned in a cavity inside the plunger assembly, and B.further including means for conducting refrigerant from the cartridge tothe cavity so that the coil is bathed in refrigerant. 5. The probedefined in claim 1 A. wherein the capillary tube coil is positionedinside the plunger assembly, and B. means for isolating the coil fromcold refrigerant gas exhausting from the probe tip. 6. The probe definedin claim 1 wherein the outer end of the probe tip has a roughened outersurface to increase adherence of the tip to frozen tissue.

7. A self-contained cryosurgical probe comrising A. a pencil-likehousing, B. a refrigerant-containing cartridge positioned in thehousing, C. a hollow, thermally conductive tip projecting from one endof the housing, D. a small diameter capillary tube having 1. one endpositioned inside the tip near said outer end,

2. the other end thereof positioned in the housing opposite thecartridge, and

3. a substantial length intermediate said ends formed into a smalldiameter multi-turn coil,

E. means for opening the cartridge to release the refrigerant inside thecartridge which thereupon flows through the capillary tube to the probetip and thence exhausts therefrom to the atmosphere, and

F. means for controlling the temperature of the refrigerant flowing tothe tip so as to stabilize its mass flow rate so that the probe canoperate for a maximum period of time on the refrigerant in thecartridge.

8. The probe defined in claim 7 wherein the outer surface of the probetip has indentations which increase the adherence of the tip to frozentissue.

9. The probe defined in claim 7 and further including means on the innerend of the probe tip which co-act with the housing to prevent rotationand translation of the tip relative to the housing.

10. The probe defined in claim 7 and further including means coveringthe probe tip except at its outer end for preventing adherence to frozentissue.

11. The probe defined in claim 7 wherein the temperature controllingmeans comprise means for isolating the capillary tube from coldrefrigerant exhausting from the probe tip.

12. The probe defined in claim 11 wherein the isolating means comprisemeans for conducting liquid refrigerant from the cartridge to thecapillary tube coil so that the refrigerant surrounds the outside of thecoil.

13. The probe defined in claim 7 wherein the cartridge opening-meanscomprise A. a rigid hollow member positioned in the housing opposite thecartridge,'the inside of said member communicating. with the other endof the capillary tube, and

B. means accessible from the outside of the housing for moving thecartridgeand rigid member relative to one another so that the rigidmember penetrates the cartridge whereby the refrigerant therein flowsthrough the member to the capillary tube.

14. 'A small self-contained disposable cryosurgical probe comprising A.a pencil-like housing, I B. a refrigerant-containing cartridgepositioned in the housing, C. a hollow thermally conductive tipprojecting from one end of the housing, said tip having a closed outerend, 7 D. a hollow plunger positioned within the housing between thecartridge and the tip, E. a small diameter capillary tube, said tubehaving 1. one end thereof communicating with the plunger end adjacent tothe cartridge,

2. its other end positioned inside the tip near its outer end, and

3. a substantial length intermediate said ends formed into a smalldiameter multi-turn coil,

F. means for moving the cartridge and plunger assembly relative to oneanother so that the plunger assembly opens the cartridge and releasesthe refrigerant which thereupon flows through the capillary tube to theprobe tip and thence exhausts from the tip to the atmosphere, and

G. means for stabilizing the temperature of the refrigerant flowingthrough the capillary tube so as to maintain a substantially uniformmass flow rate of refrigerant through the capillary tube to the tip.

15. The probe defined in claim 14 wherein the temperature stabilizingmeans A. control the point in the capillary tube at which therefrigerant starts to boil, and

B. maintain two-phase flow of refrigerant from said point to the probetip throughout substantially the entire operating time of the probe.

16. Small disposable self-contained cryosurgical probe comprising A. apencil-like housing, B. a cartridge positioned in the housing, saidcartridge having a volume less than 12cc, C. a hollowthermally-conductive tip projecting from one end of the housing, saidtip having a closed outer end, D. a small diameter capillary tube, saidtube having 1. one end positioned inside the tip near its outer end,

2. its other end positioned in the housing opposite the cartridge, and

3. a substantial length intermediate said ends formed into a smalldiameter multi-turn coil,

E. means for conducting refrigerant from said cartridge to saidcapillary tube so that the refrigerant flows directly to the outer endof the tip, and

F. means for controlling the mass flow rate of the refrigerant throughthe capillary tube so that the refrigerant cools the tip end primarilyby evaporation right at the tip end to a temperature that is low enoughto cause the tip end to adhere to tissue in a room temperatureenvironment in less than 6 sec- 3. a relatively long length intermediatethe ends formed into a mult-turn coil. E. means for venting the tip tothe atmosphere. I. means for opening the cartridge so that refrigerantflows through the tube to the tip, and G. means for stabilizing thetemperature of the refrigerant flowing through the tube to the probe tipso that the point in the tube at which the refrigerant boils remainssubstantially the same until the cartridgc is empty of refrigerant.

18. The probe defined in claim 17 wherein the stabilizing means causethe refrigerant to boil at a location in the tube between and along thelength of the tube

1. A self-contained cryosurgical probe comprising A. a pencil-likehousing, B. a refrigerant-containing cartridge slidably positioned inthe housing, C. a hollow, thermally conductive tip projecting from oneend of the housing, D. a plunger assembly positioned within the housingbetween the cartridge and the tip, E. a small diameter capillary tubeconnected to the plunger assembly, said tube having
 1. one end thereofcommunicating with the plunger end adjacent to the cartridge,
 2. itsother end positioned inside the tip near its outer end, and
 3. asubstantial length intermediate its said ends formed into a smalldiameter multi-turn coil, F. means on the plunger assembly for openingthe cartridge when the cartridge is slid toward the plunger assembly,and G. means for sliding the cartridge toward the plunger so that theplunger opens the cartridge and releases the refrigerant which thereuponflows through the capillary tube to the probe tip and cools the tip. 2.its other end positioned inside the tip near its outer end, and
 2. itsother end extending into the housing opposite the cartridge, and
 2. itsother end positioned in the housing opposite the cartridge, and
 2. itsother end positioned inside the tip near its outer end, and
 2. the otherend thereof positioned in the housing opposite the cartridge, and
 2. Theprobe defined in claim 1 wherein A. the cartridge has a removable plugin the end of the cartridge opposite the plunger, and B. the plungerassembly opens the cartridge by pushing the plug into the cartridge. 3.a substantial length intermediate its said ends formed into a smalldiameter multi-turn coil, F. means on the plunger assembly for openingthe cartridge when the cartridge is slid toward the plunger assembly,and G. means for sliding the cartridge toward the plunger so that theplunger opens the cartridge and releases the refrigerant which thereuponflows through the capillary tube to the probe tip and cools the tip. 3.The probe defined in claim 2 A. wherein the cartridge has an internalshoulder in the end thereof containing the plug, and B. the plug hasflexible resilient arms formed on the end of the plug inside thecartridge, said arms engaging behind the shoulder to prevent blow out ofthe plug due to pressure inside the cartridge above atmospheric.
 3. asubstantial length intermediate said ends formed into a small diametermulti-turn coil, E. means for opening the cartridge to release therefrigerant inside the cartridge which thereupon flows through thecapillary tube to the probe tip and thence exhausts therefrom to theatmosphere, and F. means for controlling the temperature of therefrigerant flowing to the tip so as to stabilize its mass flow rate sothat the probe can operate for a maximum period of time on therefrigerant in the cartridge.
 3. a substantial length intermediate saidends formed into a small diameter multi-turn coil, E. means forconducting refrigerant from said cartridge to said capillary tube sothat the refrigerant flows directly to the outer end of the tip, and F.means for controlling the mass flow rate of the refrigerant through thecapillary tube so that the refrigerant cools the tip end primarily byevaporation right at the tip end to a temperature that is low enough tocause the tip end to adhere to tissue in a room temperature environmentin less than 6 seconds and maintains the tip end temperature for aduration in excess of 1.5 minutes.
 3. a substantial length intermediatesaid ends formed into a small diameter multi-turn coil, F. means formoving the cartridge and plunger assembly relative to one another sothat the plunger assembly opens the cartridge and releases therefrigerant which thereupon flows through the capillary tube to theprobe tip and thence exhausts from the tip to the atmosphere, and G.means for stabilizing the temperature of the refrigerant flowing throughthe capillary tube so as to maintain a substantially uniform mass flowrate of refrigerant through the capillary tube to the tip.
 3. arelatively long length intermediate the ends formed into a mult-turncoil, E. means for venting the tip to the atmosphere, F. means foropening the cartridge so that refrigerant flows through the tube to thetip, and G. means for stabilizing the temperature of the refrigerantflowing through the tube to the probe tip so that the point in the tubeat which the refrigerant boils remains substantially the same until thecartridge is empty of refrigerant.
 4. The probe defined in claim 1 A.wherein the capillary tube coil is positioned in a cavity inside theplunger assembly, and B. further including means for conductingrefrigerant from the cartridge to the cavity so that the coil is bathedin refrigerant.
 5. The probe defined in claim 1 A. wherein the capillarytube coil is positioned inside the plunger assembly, and B. means forisolating the coil from cold refrigerant gas exhausting from the probetip.
 6. The probe defined in claim 1 wherein the outer end of the probetip has a roughened outer surface to increase adherence of the tip tofrozen tissue.
 7. A self-contained cryosurgical probe comrising A. apencil-like housing, B. a refrigerant-containing cartridge positioned inthe housing, C. a hollow, thermally conductive tip projecting from oneend of the housing, D. a small diameter capillary tube having
 8. Theprobe defined in claim 7 wherein the outer surface of the probe tip hasindentations which increase the adherence of the tip to frozen tissue.9. The probe defined in claim 7 and further including means on the innerend of the probe tip which co-act with the housing to prevent rotationand translation of the tip relative to the housing.
 10. The probedefined in claim 7 and further including means covering the probe tipexcept at its outer end for preventing adherence to frozen tissue. 11.The probe defined in claim 7 wherein the temperature controlling meanscomprise means for isolating the capillary Tube from cold refrigerantexhausting from the probe tip.
 12. The probe defined in claim 11 whereinthe isolating means comprise means for conducting liquid refrigerantfrom the cartridge to the capillary tube coil so that the refrigerantsurrounds the outside of the coil.
 13. The probe defined in claim 7wherein the cartridge opening means comprise A. a rigid hollow memberpositioned in the housing opposite the cartridge, the inside of saidmember communicating with the other end of the capillary tube, and B.means accessible from the outside of the housing for moving thecartridge and rigid member relative to one another so that the rigidmember penetrates the cartridge whereby the refrigerant therein flowsthrough the member to the capillary tube.
 14. A small self-containeddisposable cryosurgical probe comprising A. a pencil-like housing, B. arefrigerant-containing cartridge positioned in the housing, C. a hollowthermally conductive tip projecting from one end of the housing, saidtip having a closed outer end, D. a hollow plunger positioned within thehousing between the cartridge and the tip, E. a small diameter capillarytube, said tube having
 15. The probe defined in claim 14 wherein thetemperature stabilizing means A. control the point in the capillary tubeat which the refrigerant starts to boil, and B. maintain two-phase flowof refrigerant from said point to the probe tip throughout substantiallythe entire operating time of the probe.
 16. Small disposableself-contained cryosurgical probe comprising A. a pencil-like housing,B. a cartridge positioned in the housing, said cartridge having a volumeless than 12cc, C. a hollow thermally-conductive tip projecting from oneend of the housing, said tip having a closed outer end, D. a smalldiameter capillary tube, said tube having
 17. A disposableself-contained cryosurgical probe comprising A. a pencil-like housing,B. a refrigerant-containing cartridge in the housing, C. a hollow tipprojecting from one end of the cartridge, said tip having a closed outerend, D. a capillary tube having
 18. The probe defined in claim 17wherein the stabilizing means cause the refrigerant to boil at alocation in the tube between 70 and 90% along the length of the tube.